1. Field of the Invention:
The invention relates in general to elevator systems, and more specifically to traction elevator systems having a DC drive motor and an adjustable voltage source.
2. Description of the Prior Art:
In elevator systems of the traction type having a DC drive motor connected to an adjustable voltage source, such as to a solid state dual bridge converter, or a motor-generator set, it is desirable to monitor the voltage, and the rate of change of voltage, in the armature circuit. It is important that the armature voltage be below a predetermined magnitude when the elevator car is in the process of landing, i.e., stopping at a target floor, especially after the car doors and hatch doors have started to open. It is also important that the rate of change of armature voltage, which is representative of acceleration of the motor and elevator car, be below a predetermined magnitude at all times.
While voltage and acceleration monitoring have been used in the prior art, such arrangements have utilized custom designed transformers, high voltage resistors, and high voltage capacitors, to provide the armature voltage and rate-of-change signals. It would thus be desirable to be able to eliminate custom components, and to reduce the size of the components to the point where the monitoring functions are suitable for PCB mounting in a printed circuitboard cage. Any change to these monitoring functions, however, must not be to the detriment of reliability.